Graham Stuart Thomas, a horticulturalist, author and botanical artist who was considered by many garden experts as one of the most influential gardeners of the 20th century, died April 17 in a hospital near his home in Woking, south of London. He was 94 and had been hospitalized with pneumonia.
In his eight decades as a "plantsman," Thomas retrieved a number of flower varieties from extinction and restored the grounds of more than 100 historic houses when he served as advisor to the National Trust, a preservationist group in Britain.
A graceful and informative writer, Thomas published 19 books on plants, which he illustrated with his own watercolors and drawings. Most often he wrote about roses, starting with "Old Shrub Roses" (1955). The book was the result of several decades spent collecting and propagating so-called old roses that he acquired from private homes and plant nurseries throughout Europe. By the end of the Edwardian era, those roses had fallen out of fashion in favor of more prolific hybrids.
"Thomas set about preserving the heritage of old roses when many of them were on the verge of extinction," said Clair Martin, rose curator at the Huntington Botanical Gardens in San Marino.
"There were several hundred examples of them between 1800 and 1850, but only a few by the time he began to collect and restore them," Martin said. "He established a baseline on the subject. To learn the history of a particular rose, or how it grows, I refer to his books."
Experts also credit Thomas for his work in perennials, alpine plants, groundcovers and decorative shrubs. His books on those topics are standard references.
"Any serious gardener will tell you that his 'Perennial Garden Plants' (1976) is the most useful thing in their potting shed," said Ngaere Macray, publisher of Sagapress in Long Island, N.Y., a friend of Thomas for more than 20 years. She reissued a number of his early books and also published his most recent: "The Garden Through the Year," written when he was 93. (The books are distributed by Timber Press.)
"Graham probably knew the characteristics of more plants than anyone has ever known," Macray told The Times this week. In an appendix to "The Complete Flower Paintings" (1987), Thomas identifies the more than 600 plants he had propagated by then.
Thomas was born in Cambridge, England, in 1909 into a family of amateur gardeners and musicians. He sang with a madrigal group for 40 years.
When he was 6, his godfather gave him a blossoming fuchsia, which opened him up to the possibilities of a life in the garden. At 17, he became a volunteer at the Cambridge University Botanic Garden, which allowed him to attend campus lectures on botany and horticulture. They were his only formal education in horticulture.
Within four years he was foreman at T. Hilling & Co, a 300-acre wholesale nursery in Surrey, where he met Gertrude Jekyll, already famous for her artistic use of color in the garden. Jekyll became a mentor to Thomas and gave him a way of looking at his own work.
"Graham always said that gardening is an art, not a science," Macray said. "He saw it as a place where people can express their unique artistic talents."
Thomas was made director of Hilling nursery in the early 1940s, and from then on he made the conservation of plants his ongoing concern. For him it was an aspect of British cultural history.
After World War II, Thomas and a friend, James Russell, took over Sunningdale Nursery, west of London, which became known as the most beautiful nursery in the country.
When garden enthusiasts established the National Trust in 1948 and acquired their first private home, they asked Thomas to restore the grounds. A few years later, he was named gardens advisor to the National Trust, a position he held until 1974. After he retired he continued as a consultant to the group, overseeing the maintenance of 110 public gardens in England, Scotland and Ireland.
Thomas said he was most proud of his most personal work, for Mottisfont Abbey, a former Augustinian priory in Hampshire where he planted his own collection of old roses in what had been the monks' kitchen garden.
"I like to think that the rose's pomp will be displayed far into the future at Mottisfont," he wrote in his notes about the project. He hoped it would also be the place "where my work of some 30 years collecting these varieties from France, Germany and the United States -- and numerous gardens and nurseries in the British Isles -- will not be set at naught."
He was a lifelong bachelor with an Old World manner that showed itself even in his prose.
He referred to rose hips, the round part of the buds, as "rose heps." The more typical term was meant to suggest the shape of a woman's figure. Thomas respectfully chose to avoid such easy familiarity.
He lived in a small house, Briar Cottage, with two upright pianos in the living room and surrounded by a large number of awards for his work.
The most notable of them is the Order of the British Empire, which was presented to him in 1975 for his decades of service to his country.
His front and back gardens at Briar Cottage displayed about 1,500 varieties of plants, including 20 kinds of roses as well as assorted climbers that covered the fences and the walls of the house.
Daffodils, irises and roses were his favorite flowers, he said.
Thomas was an avid letter writer who answered eight or 10 inquiries a day, and promptly wrote thank-you notes in longhand. He also wrote his books by hand.
During his lifetime he was honored by several expert gardeners who named flowers for him.
The Graham Thomas Rose is a modern hybrid resembling an old rose with large, deep yellow, cabbage-like blossoms.
Thomas is survived by one nephew.